Manage wisely your cache setting in Cephedit24 Nov 2014
Today we discuss how to manage wisely your cache setting in Ceph (ceph.com/docs/master/rbd/rbd-config-ref/). The type of cache discussed below is the user space implementation of the Ceph block device (i.e.,
Suddenly after migration to Ceph we start observing the doubling of memory usage by every virtual machine.
After some research we found the configuration error in
ceph.conf. The option
rbd cache size describes the amount of cache reserved for every virtual disk, so the total amount of RAM reserved for cache is given by
After some rational reasoning of the kind - the standard hard drive usually possess
64M of cache - the final version of configuration will be the following
Now push the configuration to the virtual hosts
To apply settings without virtual machine restart use
KVM live migration. After the virtual machine is migrated from
host2 the new process will start taking into account the modification to the ceph configuration.
If not sure about setting leave Ceph's default values for amount of cache, simply enable it